The present invention relates generally to circuit breakers, and more particularly to multipole rotary contact circuit breakers having a stop mechanism arrangement.
Typical circuit breakers are overcurrent protective devices used for circuit protection and isolation. The basic function of a circuit breaker is to provide electrical system protection whenever an electrical abnormality occurs in any part of the system. In a rotary contact circuit breaker, current enters the system from a power line. The current passes through a load strap to a stationary contact fixed on the strap and then to a movable contact. The movable contact is fixedly attached to a contact arm, and the contact arm is typically secured to a rotor that in turn is rotatably mounted in an electrically insulative cassette. As long as the fixed contacts are in physical contact with the movable contacts (this position defined as the CLOSED position), the current passes from the fixed contacts to the movable contacts and out of the circuit breaker to downline electrical devices.
Rotary contact circuit breakers are typically stored and shipped in the OPEN position. The OPEN position refers to the position of the contacts in which the stationary contacts and the movable contacts are not in direct physical contact with each other. In addition, the OPEN position allows the contact arms to be in physical contact with rebound bumpers. These rebound bumpers serve to absorb the impact energy of the contact arm when the contact arm moves independently of the rotor upon introduction of a high current in the circuit breaker (also know as the BLOWN OPEN position). In some instances, continuous contact between the contact arm and the rebound bumpers results in creep deformation of the rebound bumpers or a fusing of the rebound bumpers to the contact arm thereby restricting movement of the contact arm from the OPEN to the CLOSED position.
Accordingly, there is a need in the art for a circuit breaker having improved contact control between stationary and moving components.
One embodiment of the present invention comprises a circuit breaker comprising a contact arm movable between a closed position, an open position and a blown open position wherein the contact arm is disposed in the circuit breaker. A bumper is disposed to contact the contact arm when the contact arm is in the blown open position. In addition, a stop member is disposed to be in contact with a linkage assembly so as to create a gap between the bumper and the contact arm when the contact arm is disposed in the open position.